Technical Abstract: Land application of liquid manure and agricultural wastes to agricultural land is a widely used BMP, however application to crop fields with subsurface drainage may result in rapid movement to the drains and surface water. In the 4-year period, 2000 to 2003, ninety-eight Ohio incidents were recorded where manure wastes flowed through agricultural subsurface drains (tile drains) to contaminate streams. We investigated these reports to determine the factors that contributed to these violations. Violations occurred most frequently with land application of liquid swine or dairy manure wastes. Deep cracks in the soil, old root channels, earthworm burrows, and loamy soils promoted preferential flow of manure to drain lines and to surface waters. Violations occurred with all methods of application – irrigation, surface spreading, and subsurface injection. Multiple factors contributed to most incidents. Farm operators accounted for 63 manure violations and custom applicators one-fourth (26). Most operators did not have approved manure management plans (58 operations). Twenty-eight (72%) of the 39 operations that had a manure management plan did not follow their plans. Saturated soils or heavy rainfall (41 cases) was the most common factor cited. Lack of manure storage management, over application, equipment failures, and broken/shallow tile were other major factors identified. Avoiding these conditions should reduce the number and severity of incidents. Tillage may reduce movement of liquid manure contamination to subsurface drains by disrupting soil macropores, but 17% of the incidents occurred on soils that were tilled. The lack of proper manure application was a key factor in most manure violations.